title: Control of dorsoventral somite patterning by Wnt-1 and beta-catenin.
abstract: In vertebrates, the dorsoventral patterning of somitic mesoderm is controlled by factors expressed in adjacent tissues. The ventral neural tube and the notochord function to promote the formation of the sclerotome, a ventral somite derivative, while the dorsal neural tube and the surface ectoderm have been shown to direct somite cells to a dorsal dermomyotomal fate. A number of signaling molecules are expressed in these inducing tissues during times of active cell fate specification, including members of the Hedgehog, Wnt, and BMP families. However, with the exception of the ventral determinant Sonic hedgehog (Shh), the functions of these signaling molecules with respect to dorsoventral somite patterning have not been determined. Here we investigate the role of Wnt-1, a candidate dorsalizing factor, in the regulation of sclerotome and dermomyotome formation. When ectopically expressed in the presomitic mesoderm of chick embryos in ovo, Wnt-1 differentially affects the expression of dorsal and ventral markers. Specifically, ectopic Wnt-1 is able to completely repress ventral (sclerotomal) markers and to enhance and expand the expression of dorsal (dermomyotomal) markers. However, Wnt-1 appears to be unable to convert all somitic mesoderm to a dermomyotomal fate. Delivery of an activated form of beta-catenin to somitic mesoderm mimics the effects of Wnt-1, demonstrating that Wnt-1 likely acts directly on somitic mesoderm, and not through adjacent tissues via an indirect signal relay mechanism. Taken together, our results support a model for somite patterning where sclerotome formation is controlled by the antagonistic activities of Shh and Wnt signaling pathways.
authors.affiliation: Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: J
authors.initials: J
authors.lastname: Capdevila
authors.forename: C
authors.initials: C
authors.lastname: Tabin
authors.forename: R L
authors.initials: RL
authors.lastname: Johnson
mesh_terms: D000818:Animals; D015415:Biomarkers; D019521:Body Patterning / Q000187:drug effects; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis; D002454:Cell Differentiation / Q000502:physiology; D002642:Chick Embryo; D003598:Cytoskeletal Proteins / Q000378:metabolism / Q000502:physiology*; D018076:DNA, Complementary / Q000096:biosynthesis; D015536:Down-Regulation / Q000235:genetics / Q000502:physiology; D053823:Hedgehog Proteins; D051379:Mice; D017570:MyoD Protein / Q000096:biosynthesis; D014176:Protein Biosynthesis; D011506:Proteins / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000502:physiology*; D019170:Somites / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015534:Trans-Activators; D051153:Wnt Proteins; D051155:Wnt1 Protein; D014981:Xenopus; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: D015415:Biomarkers; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; C495266:CTNNB1 protein, Xenopus; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D053823:Hedgehog Proteins; D017570:MyoD Protein; D011506:Proteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; C495249:WNT1 protein, Xenopus; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C525812:bmp4 protein, Xenopus; C525813:bmp4 protein, zebrafish